The present invention relates to a packaging machine for packing cigarettes or other articles, and more particularly to a paper pressing device to be used for an arbour turret packaging machine.
This invention is suitably applicable to the type of a machine which makes a well known soft pack or cigarette bucket to be used for cigarette packing from soft and not thick material such as wrapping paper by winding it around the periphery of an arbour. It particularly provides a device for folding the packing material in a space defined between one of the lateral faces of the arbour and a pressure plate positioned opposite thereto as well as opening and closing mechanisms.
An arbour turret for this type of packaging machine has a plurality of arbours on its circumference at equal spaces and is formed in disc shape. The arbour turret is turned in a stepping manner on its center axis and moved intermittently. A packing paper supplying device or feeder is provided at a fixed position adjacent the arbour turret. The term "packing paper" used herein refers to packing material which is commonly used for a soft pack, such as aluminum foil for making an inner pack and outer wrapping paper. However, other material may be used. According to the above mentioned type of a packaging machine, the aluminum foil and outer wrapping paper are supplied by different feeders located at different positions.
The aluminum foil is supplied along one of the lateral faces of the arbour and wound around its four faces to form a sleeve shape. One end of the sleeve shaped aluminum foil is folded forming a small pack having an open top at its other end.
Furthermore, in order to place said wrapping paper upon said small pack made of aluminum foil, the wrapping paper is supplied along said lateral face of the arbour and wound around the four faces thereof in the same manner as described above to form a sleeve shape, one end of which is folded in the bottom of the aluminum pack to form the outer pack. As a result, a small double pack is produced.
A cigarette supplying device or feeder is provided at a fixed place adjacent the arbour turret. Cigarettes, after processed, are orderly arranged in a bundle of three layers, i.e., 6 pieces, 7 pieces and 6 pieces from the top. Said packaging machine is equipped with a cigarette supplying device or feeder from where a bundle of cigarettes is fed into the cylindrical bore of said arbour.
Usually, the arbour turret is provided with means for adhering the overlapped portions of the small pack made of wrapping paper. If necessary, heating and cooling equipments may be provided in order to fix the portions where adhesive is applied.
The bundle of cigarettes is pushed by a pusher through an aperture on the arbour, and pushed out into the pack formed on the arbour for containing the bundle of cigarettes and discharged therefrom as a small package. However, this small package has still an open end at its top as mentioned above and the folding and sealing operations are conducted in the next process.
It is important for this type of packaging machine, which makes a small pack by means of receiving aluminum foil and wrapping paper from feeders positioned adjacent the arbour turret and winding them around the arbour, to receive the supplied packing paper on the lateral face of the arbour and hold it precisely. It is more important to hold the end portions in order to make overlapped portions on the packing paper wound around the arbour. Particularly, when plural sheets of packing paper are used, one over another, it has a vital effect on finish of the resulted product whether said holding means properly align and hold the sheets.
Because of the above mentioned reasons, various proposals have been presented for improving the device. One such successful improvement is described in detail in the specification of Japanese Patent Application No. 57-24508 filed by the present applicant.
It discloses an arbour turret packaging machine which comprises an arbour turret being arranged in disc shape and caused to turn in a stepping manner, means for supplying packing paper to one of lateral faces of the arbour, means for folding the packing paper into a small pack which is wound around said arbour, means for holding the packing paper on the lateral faces of said arbour, whereby said holding means comprises presser plates being positioned opposite the lateral faces of the arbour, lever means provided at one ends of said presser plates, a disc cam to actuate said lever means and oscillating means for turning the disc cam forwardly and backwardly for a predetermined angle.
In recent years, the production speed or turning speed of this type of packaging machine has been rapidly increased. As a result, a new problem is created for the machine. More specifically, as the turning speed of the machine increases, the force of inertia to be produced in the arbour turret is rapidly increased. That is to say, the pressing force of the presser plates is varied. When the arbour turret starts and stops, the pressure on the outside of the arbour is weakened. In an extreme case, the pressure is entirely lost, thus making the presser plates unable to hold the packing paper, particularly the overlapped portions.
The present invention is accomplished in order to overcome the above mentioned disadvantages by eliminating the variation of pressure caused by the force of inertia and provides a stable packaging machine which is operable at high speed.
It is possible for the arbour turret to choose a motion curve out of various modes along which it turns. However, no matter which mode is selected, it is impossible for the turret to completely eliminate the angular acceleration which is inevitably produced by turning motion. Once the angular acceleration is produced in an object having mass, the turning effect, which is equal to the product of the inertia moment of the object and its angular acceleration, is produced. This is apparent from Newton's law.
Heretofore, the presser plates of the arbour turret are arranged such that they are opened and closed forwardly and backwardly in the progressing direction. Therefore, the presser plates having mass are directly affected by angular acceleration.
The pressure of the presser plates on the outer faces of the arbour is caused by a resilient spring. However, the angular acceleration, which is given to the presser plates, tends to open and close the presser plates on their axes because of the turning effect. As a result, the force given by the spring competes with that given by the angular acceleration, thus producing effect caused by the mutual force relation. That is to say, when the force of inertia caused by angular acceleration is superior, the pressing force of the presser plates becomes minus and loses their functions. It is known that angular acceleration is not only given in the plus direction but also in the minus direction. If minus angular acceleration is given, the pressing force of the plesser plates is multiplied and becomes excessive. As a result, the arbour is damaged. This explanation is also applicable to the other presser plate which is provided at a position symmetric with respect to the above mentioned presser plate, and which is caused to press one of the arbour faces in the reversed direction.